Method of reshaping fabricated infrared-generating devices such as electric lamps and the like



March 14, 1967 s. M. DRANGEID 3,309,187

METHOD OF RESHAPING FABRICATED INFRARED-GENERATlNG DEVICES SUCH AS ELECTRIC LAMPS AND THE LIKE Filed Dec. 30, 1965 INVENTOR. SIVERT MY DRANGEID FIG. 7.

United States Patent Westing- Pittsburgh, Pa., :1 corpora- This invention relates to electric lamps and has particular reference to a method of altering the configuration of a previously fabricated electric incandescent lamp.

Tubular incandescent lamps of high wattage rating are presently being marketed in large numbers for both heating and lighting applications. These lamps are commonly referred to as T3 quartz infrared or heat lamps and consist of a tubular quartz envelope containing a coiled tungsten filament that is held in coaxial relationship with the envelope by a series of spaced disks or support wires. The filament is energized by means of leads that are embedded in press seals provided at each end of the envelope. The lamps are very compact and are made in sizes ranging from 500 watts and up. Lamps of this type are disclosed in U.S. Patent No. 2,864,025, issued to A. G. Foote et al. on Dec. 9, 1958.

It would be very desirable in many applications to have lamps of the aforementioned type that are of arcuate rather than linear configuration so as to concentrate more light and heat in a given area, for example. However,

I T3 lamps of non-linear configuration have heretofore not been marketed since it would be impractical from both a cost and engineering standpoint to insert and then position the filament-and-support assembly in an envelope having a bent or arcuate portion. For this reason, all of the T3 lamps now being marketed are of linear configuration. The only exception is the recent development of a lamp of this type wherein the ends of the envelope containing the lead-in conductors are bent away from the body portion of the lamp which contains the filament so as to provide a pair of rearwardly projecting arms or extensions. A lamp of this construction is disclosed in U.S. Patent No. 3,080,497, issued Mar, 5, 1963, to E. B. Noel et al. Such bent end lamps, however, inherently present the same problem which prompted the present invention in that the body portion of the lamp contains the filament and constitutes the radiation-generating portion is still of linear configuration as in the other prior art lamps.

The term linear as used herein means straight as opposed to curved or crooked, and the expression arcuate configuration includes shapes that have both curved and straight segments, as in the letter M or B, for example.

In view of the foregoing, it is the general object of the present invention to provide a simple inexpensive method for manufacturing infrared ray generating devices, such as electric incandescent lamps or the like, of non-linear configuration.

Another object is the provision of an efiicient method for bending a previously fabricated tubular incandescent lamp into various arcuate shapes without damaging the lamp or impairing its performance.

Briefly, the foregoing and other objects which will become apparent to those skilled in the art as the description proceeds are achieved in accordance with the present invention by covering the portion of the envelope that is to be bent with a suitable noncombustible insulating material and then operating the lamp at a power input and for a period of time such that the covered portion of the envelope is softened solely by the heat generated by the filament. While the lamp is still energized, the heatsoftened covered portion of the envelope is bent, pref- 3,39,187 Patented Mar. 14, 1967 erably with the help of a suitable form or template, into the desired configuration. The lamp is then de-energized and allowed to cool, with or without the covering of insulating material, thereby rigidifying the bent portion of the envelope and setting the lamp in its new configuration. Thus, the heat generated by the energized filament is utilized in accordance with the invention to soften the envelope so that the lamp can be bent into the desired configuration after it is fabricated thereby completely avoiding the many production problems that would be encountered if the envelopes were bent into the desired configuration before the lamp was assembled.

A better understanding of the invention will be obtained by referring to the accompanying drawing, wherein:

FIGURE 1 is a side elevational view, partly in section, of a U-shaped T3 quartz lamp manufactured in accordance with the present invention;

FIGS. 2 and 3 are perspective and side elevational views, respectively, of helical and sinusoidal shaped lamps which illustrate the Wide variety of shapes afforded by the invention;

FIG. 4 is a side elevational view, partly in section, of a conventional linear T3 lamp and its associated wrapping of insulating material prior to the bending operation in accordance with one form of the invention;

FIGS. 5 and 6 are perspective views of various forms or fixtures that can 'be used to facilitate bending the softened portions of the lamp envelope into the desired configuration; and,

FIG. 7 is a side sectional view of an alternative arrangement for softening the completed lamp and bending it into the desired shape in accordance with the invention.

While the invention can be used'to alter the configuration of various types of electrical devices that have vitreous envelopes and generate a sufiicient amount of heat during operation, it is especially adapted for use in conjunction with double-ended electric incandescent lamps having tubular envelopes and it has, accordingly, been so illustrated and will be so described.

In FIG. 4 there is shown a double-ended elongated T3 lamp 10 comprising a tubular substantially straight envelope 12 of quartz or the like that contains a longitudinally extending coiled tungsten filament 13 which is attached to lead-in conductor assemblies 16 hermetically embedded in press seals 18 provided at each end of the envelope. The filament is held in substantially coaxial position within the envelope by a series of spaced supporting members 14 such as tantalum disks or tungsten wire loops.

Before the envelope is tipped off during fabrication it is evacuated and filled with a suitable inert gas, such as argon, at a pressure slightly below atmospheric, as for example around 600 mm. to 700 mm. of mercury. The filament is so designed that it operates at a brightness temperature of approximately 2600 K. and the wattage and dimensions of the lamp are so correlated that the envelope 12 reaches a temperature of about 700 C. when the lamp is operated in open air at normal room temperature. The fill gas pressure, accordingly, increases when the lamp is operated. If the aforementioned fill pressure of 600 mm. to 700 mm. is used, the pressure increases to around 3 atmospheres during the operation of the lamp. Thus, lamps of this type are so designed that the envelope inherently reaches a temperature above 500 C. and the fill pressure exceeds atmosphere pressure when the lamp is operated at its rated voltage. A detailed description of a tubular infrared ray generating lamp of this type and its operating characteristics are set forth in the aforementioned Foote et al. Patent No. 2,864,025.

Bending of the initially straight tubular lamp 10 is accomplished in accordance with one embodiment of the a present invention by wrapping a selected intermediate portion of the envelope 12 with a suitable non-combustible insulating material that will not adhere to softened quartz, such as asbestos cloth or the like, to form a covering or sheath 21 that encloses this portion of the envelope, as shown in FIG. 4. Satisfactory results have been achieved by Wrapping six or seven layers of asbestos cloth around the envelope, the cloth being of such thickness that the overall thickness of the sheath 21 is approximately /2 inch.

After the wrapping operation has been completed, the lamp 10 is energized by connecting the terminal wires 29 at each end of the lamp to a suitable voltage source through conductors 22 and 23, as shown in FIG. 4. The lamp is preferably operated at substantially its rated voltage for at least 1 to 1 /2 minutes. The section of the envelope l2 enclosed by the asbestos sheath 21 is, of course, heated to a much higher temperature than the exposed portions of the envelope and, after about 1 minute of operation, reaches a temperature such that the quartz softens and becomes sufficiently plastic to allow the envelope to be bent into the desired configuration. Quartz begins to sag at around 1500 C. so that the temperature of the covered portion of the envelope prior to bending is in the order of about 1200 C. to 1500" C.

Thus, to form a U-shaped lamp Ilia of the type shown in FIG. 1, the superheated central portion of the tubular lamp 10 and its insulating sheath 21 are simply bent, while the lamp is still energized, into a 180 arc. Surprisingly, it has been found that the lamp can be bent in this manner into a smooth are without constricting the envelope or producing any strains or irregularities at the bend. The superatmospheric pressure of the heated fill gas, of course, operates to prevent any wrinkling or sagging of the quartz. However, in order to insure that the filament 13a is not forced against the inner surface of the envelope 12a as a result of the bending operation, the spacing between the support members 14a in the region of the bend is made such that at least three supports are located in the bend, as shown in FIG. 1.

After the lamp 10a has cooled and become set in its new configuration the wrapping 21 of insulating material is removed.

It is important that the bending of the envelope 12 be accomplished without elongating or contracting the softened portion in any way insofar as this would cause the filament to stretch or buckle and impair the lamp quality. As shown in FIG. 1, U-shaped lamps 19a having three support members 14a located at the bend can readily be made in accordance with this invention without distorting the filament 13a in any manner or displacing it from its original coaxial relationship with the envelope.

By using a suitable form or template and enclosing substantially the entire lighted length of the envelope, helical shaped lamps 10b of the type shown in FIG. 2 can also be made. Other shapes are possible. For example a sinusoidal or M-shaped lamp We of the type shown in FIG. 3 can be fabricated by applying a wrapping of suitable insulating material around the envelope at a plurality of points and then sequentially bending these portions around a suitable form after they have become softened by operating the lamp for the required period of time.

In FIG. there is shown a fixture 24 which will facilitate bending the softened envelope into the Ushaped or sinusoidal configurations illustrated in FIGS. 1 and 3, respectively. This fixture comprises a base or bed plate 25 having three upstanding cylindrical posts 26, 2'7 and 2-8 that are rigidly attached to the bed plate and spaced suitable distances apart. Both the posts and bed plate are fabricated from a suitable noncombustible material such as glass rock or the like. Glass rock is a well known refractory material available commercially and consists of 99.8% fused silica, the major impurity present being A1 0 The diameters of the posts are such that when the softened central portion of a straight lamp is bent 4 around one of the posts the lamp will have the desired U- shape indicated by the broken line a in FIG. 5. On the other hand, if the softened portions of the energized lamp are bent around post 26, then post 27 and finally post 28 the lamp will have a sinusoidal shape as indicated by the broken line c in FIG. 5.

A helical lamp 10b of the type shown in FIG. 2 can be readily fabricated by using a fixture 30 of the type i1- lustrated in FIG. 6 wherein a single cylindrical post 31 of much larger diameter is fastened to a suitable base plate 52. The desired helical configuration, indicated by the broken line b in FIG. 6, is achieved by bending the softened portion of the lamp envelope around the post 31 to form a plurality of evenly spaced turns.

The present invention is not limited to the use of wrappings of insulating material to achieve the required softening of the envelope but also encompasses the use of nonadhering granular insulating material. An arrangement for practicing the invention using this type material is illustrated in FIG. 7 and, as there shown, consists of a suitable receptacle 34 that is open at the top and is provided with a cylindrical form 35 that is fabricated from heatresistant material and extends laterally from a wall of the receptacle. The receptacle is filled with a suitable granular noncombustible insulating material 36, such as particles of glass rock, so that the form 35 is completely covered.

In accordance with this embodiment, the previously fabricated linear lamp 10 is placed at the bottom of the receptacle beneath the form and is thus completely covered by the insulating material. The terminal wires 20 of the lamp are then connected by suitable conductors 22 and 23 to a voltage supply as before and the lamp is again operated with a power input and for a period of time suificient to render the envelope plastic enough for the bending operation. The lamp terminals 20 are then gripped by suitable tools 38 and 39 and pulled upwardly so as to raise the lamp against the form 35 and bend it through an are that transforms the straight lamp 10 into a U-shaped lamp 10a (shown in dotted outline) for example. The lamp is then de-energized and allowed to cool until the envelope becomes rigid at which time the lamp is withdrawn from the receptacle.

It will be appreciated from the foregoing that a simple inexpense method for fabricating incandescent tubular lamps of non-linear configuration has been provided which not only obviates the manufacturing difficulties associated with the use of preformed envelopes but enables completely fabricated lamps to be bent into a variety of shapes on a mass production basis.

While several embodiments have been illustrated and described, it will be understood that various modifications can be made without departing from the spirit and scope of the invention. For example, in the event that the upward pull on the lamp terminals 20 in the arrangement shown in FIG. 7 damages the lead-in assemblies or press seals, then suitable tools can be employed to grip the ends of the lamp proper so that the bending operation can be accomplished without stressing the seals. In addition, the envelopes can be made from other vitreous materials besides quartz and the bent portions can be properly annealed in the well known manner to remove strains etc., if required.

I claim as my invention:

1. The method of altering the configuration of a fabricated electrical device that has a sealed vitreous envelope, is in operative usable condition, and generates infrared. radiation when energized, which method comprises:

covering a preselected portion of said envelope with non-combustible insulating material,

operating said device with a power input and for a period of time such that the covered portion of said envelope is softened solely by the heat generated by said device and retained by said covering of insulating material, and then bending the heat-softened portion of said envelope into the desired configuration.

2. The method of altering the configuration of a fabricated operative infrared generating device as set forth in claim 1 wherein the covered heat softened portion of said envelope is bent around a form while the device is still energized.

3. The method of reshaping a previously fabricated electric lamp that is in operative usable condition and generates infrared radiation when energized and has a sealed elongated vitreous envelope, which method comprises:

encasing a preselected portion of said envelope in noncombustible insulating material,

operating said lamp at a voltage for a predetermined period of time such that the encased portion of said envelope is heated to a plastic state solely by the infrared radiations produced by said lamp and retained by said insulating material,

bending the encased envelope portion into the desired configuration while said envelope portion is in its plastic condition, and then removing the insulating material from around said envelope and allowing the lamp to cool.

4. The method of reshaping a fabricated double-ended electric incandescent lamp that is in operative usable condition and has an elongated vitreous envelope that contains a longitudinally extending filament, which method comprises:

wrapping a predetermined portion of said envelope in non-combustible insulating material, operating said lamp at a voltage and for a predetermined period of time such that the wrapped portion of said envelope is softened solely by the heat generated by said filament and retained by said Wrapping of insulating material, bending the heat-softened portion of said envelope and wrapping of insulating material so that said lamp has the desired configuration and the length of the bent envelope portion is substantially unchanged, and then removing the wrapping of insulating material from said envelope and allowing the latter to cool.

5. The method of reshaping a fabricated double-ended elongated electric incandescent lamp that is in operative usable condition, said lamp having a tubular quartz envelope that is initially substantially straight and contains an inert fill gas and a longitudinally extending filament that is spaced from the walls of said envelope, the dimensions and wattage rating of said lamp being so correlated that the temperature of the envelope is at least 500 C. when the lamp is burned at its rated voltage, which method comprises,

wrapping a preselected intermediate portion of said envelope in non-combustible insulating material, operating said lamp at substantially its rated voltage for at least one minute so that (a) the Wrapped portion of said envelope is heated to a plastic state solely by the heat produced by the incandescent filament and retained by said wrapping of insulating material and (b) the fill gas pressure is materially increased, bending the softened portion of the envelope and its wrapping of insulating material around a form while said lamp is energized so that the lamp has the desired configuration and said envelope and filament remain in substantially the same spatial relationship, de-energizing the lamp, and then removing the wrapping of insulating material from said envelope after the latter has cooled and rigidified. 6. The method of bending a double-ended elongated incandescent lamp into predetermined arcuate configuration, said lamp having a tubular vitreous envelope that is initially substantially straight and contains a longitudinally extending filament that is held in spaced-apart relationship with the walls of said envelope, by a plurality of spaced supporting elements, which method comprises; arranging the filament-supporting elements within the lamp, during the assembly thereof, in such a manner that the number of said elements located along the portion of the lamp to be bent is sufiicient to maintain the filament in substantially the same spatial relationship with the envelope during and after the bending operation, completing the fabrication of said lamp, placing a covering of non-combustible insulating material around the portion of the finished lamp which is to be bent, operating said lamp at a voltage and a period of time such that the covered portion of said envelope is heated to a plastic state by the incandescent filament, and then bending the softened portion of said envelope into the desired arcuate configuration. 7. The method of bending a double-ended elongated electric incandescent lamp as set forth in claim 6 wherein; said envelope is filled with an inert gas prior to the bending operation, and the finished lamp is burned at a voltage and for a period of time prior to the bending operation that the fill gas pressure is materially increased and exceeds atmospheric pressure. 8. The method of bending a double-ended elongated electric incandescent lamp set forth in claim 6 wherein; the portion of said lamp which is to be bent is placed into a receptacle containing granules of non-combustible insulating material, and the envelope is bent into the desired configuration while the lamp is still operating and covered by said insulating material.

References Cited by the Examiner UNITED STATES PATENTS 2,032,077 2/1936 Thompson 264-27 2,135,775 11/1938 Walker -281 X 2,772,939 4/1956 Laico 65-1 10 X DONALL H. SYLVESTER, Primary Examiner. A. D. KELLOGG, Assistant Examiner. 

1. THE METHOD OF ALTERING THE CONFIGURATION OF A FABRICATED ELECTRICAL DEVICE THAT HAS A SEALED VITREOUS ENVELOPE, IS IN OPERATIVE USABLE CONDITION, AND GENERATES INFRARED RADIATION WHEN ENERGIZED, WHICH METHOD COMPRISES: COVERING A PRESELECTED PORTION OF SAID ENVELOPE WITH NON-COMBUSTIBLE INSULATING MATERIAL, OPERATING SAID DEVICE WITH A POWER INPUT AND FOR A PERIOD OF TIME SUCH THAT THE COVERED PORTION OF SAID ENVELOPE IS SOFTENED SOLELY BY THE HEAT GENERATED BY SAID DEVICE AND RETAINED BY SAID COVERING OF INSULATING MATERIAL, AND THEN BENDING THE HEAT-SOFTENED PORTION OF SAID ENVELOPE INTO THE DESIRED CONFIGURATION. 